The present invention relates generally to methods and systems for communicating between subscribers of different application-layer mobile communications protocols. More particularly, the present invention relates to methods and systems for establishing calls and forwarding short message service messages between ANSI IS-41 mobile subscribers and GSM mobile subscribers.
American National Standards Institute (ANSI) Interim Standard 41 (IS-41) includes application-layer protocols used to set up mobile calls and deliver short message service messages between mobile subscribers. IS-41 is the dominant standard for mobile communications in North America. The Global System for Mobile Communications (GSM) is the dominant standard in Europe. GSM networks provide services similar to those provided by ANSI networks, such as call delivery, short message service, mobility management, etc.
Because IS-41 and GSM standards each specify different messages for call setup and short message service, interworking systems have been developed. One type of interworking system that has been developed is a roaming gateway. A roaming gateway converts GSM messages to IS-41 messages and vice versa when a GSM subscriber is roaming in an IS-41 network or when an IS-41 mobile subscriber is roaming in a GSM network.
One problem with roaming gateways is that protocol conversion is performed for each message required to establish a call or deliver a short message service (SMS) message. For example, in order to deliver an SMS message from an IS-41 subscriber to a GSM subscriber, the IS-41 short message service center (SMSC) serving the IS-41 subscriber sends an IS-41 Short Message Service Request (SMSREQ) message to an IS-41 home location register (HLR). A roaming gateway receives the IS-41 SMSREQ Message, determines that the message is attempting to locate a GSM subscriber, converts the message into a GSM Send Routing Information for Short Message message, and forwards the message to a GSM HLR. The GSM HLR responds with a Send Routing Information for SM Acknowledge message that contains the MSC ID of the mobile switching center serving the intended recipient. The roaming gateway receives the Send Routing Information for SM Acknowledge message, converts the message into an IS-41 SMSREQ message containing the requested information and forwards the message to the IS-41 SMSC. This translation between GSM and IS-41 is repeated for each message transmitted between GSM and IS-41 network elements.
Translating each message required to set up a call or deliver an SMS message results in a high processing load on the translating node and increases call setup or SMS message delivery time. For example, because a roaming gateway is required to intercept and translate each message in a call flow, the roaming gateway may spend a significant amount of its processing resources on translating messages. The time required for translating each message can also increase call setup or SMS message delivery time. In addition, because the roaming gateway terminates IS-41 and GSM signaling, it is required to handle and translate error messages in both protocols. For instance, if a GSM short message service message recipient deactivates his or her mobile handset, the roaming gateway is responsible for receiving the GSM error message from the GSM MSC serving the called party, translating the error message to IS-41, and delivering the error message to the IS-41 SMSC. The roaming gateway may also be responsible for receiving a response from the IS-41 SMSC, translating the response to GSM, and forwarding the response to the serving GSM MSC. Handling and translating such error messages further increases the processing load on the roaming gateway.
Accordingly, there exists a long-felt need for improved methods and systems for setting up calls and delivering short message service messages between subscribers of different application-layer mobile communications protocols.
The present invention includes methods and systems for setting up calls and delivering short message service messages between mobile subscribers of different application-layer mobile communications protocols. As used herein, the phrase xe2x80x9capplication-layer mobile communications protocolxe2x80x9d refers to any protocol that operates at the application layer and is used for mobile call setup and short message service. Examples of application-layer mobile communications protocols include IS-41 and GSM.
According to one aspect, the present invention includes a routing node that receives either ANSI or GSM messages and emulates both HLR and MSC functionality to deliver SMS messages to a destination node without translating each message required to deliver the SMS messages. In the case where a GSM subscriber sends a short message service message to an IS-41 subscriber, the routing node receives a Send Routing Information for SM (SRI-SM) message from the SMSC serving the GSM subscriber. The routing node determines that the SRI-SM message is requesting routing information for an IS-41 subscriber. In response, rather than converting the SRI-SM message into an IS-41 SMSREQ message, the routing node responds to the SRI-SM message with an SRI-SM acknowledge message with the SMSC ID of an IS-41 SMSC stored in the mobile application part (MAP) MSC number field. The GSM SMSC that receives the SRI-SM ACK message interprets the SMSC ID as an MSC ID because of its location in the SRI-SM ACK message. As a result, the GSM SMSC sends a GSM mobile-terminated Forward Short Message (FSM) message that it believes is destined for a GSM MSC. By providing an IS-41 SMSC ID in the MSC ID field, the routing node eliminates the need for translation of the GSM SRI-SM message into an IS-41 SMSREQ message.
The routing node intercepts the mobile-terminated GSM Forward Short Message message transmitted by the GSM SMSC, determines it is destined for an IS-41 subscriber by examination of the number and maps the message to an IS-41 mobile-originated Short Message Delivery Point to Point (SMDPP) Invoke message. The routing node then forwards the mobile-originated SMDPP Invoke message to the IS-41 SMSC identified by the SMSC ID in the MSC number field. The IS-41 SMSC is responsible for delivering the message to the intended recipient. By converting the GSM mobile-terminated FSM message to a mobile-originated IS-41 SMDPP Invoke message, the routing node appears as an IS-41 MSC delivering a short message from a mobile station to the IS-41 network.
According to another aspect of the invention, the routing node is capable of forwarding IS-41-originating short message service messages to GSM subscribers without requiring translation of each IS-41 message to GSM and vice versa. In the IS-41-originating scenario, the routing node receives an SMSREQ Invoke message from an IS-41 SMSC. The routing node determines that the SMSREQ message is destined for a GSM subscriber and, in response, sends an SMSREQ Return Result message to the IS-41 SMSC. The routing node inserts its own point code and subsystem number in the SMS_Address field of the message, rather than the address of the MSC serving the intended recipient. However, because the PC and SSN values are in the SMS_Address field, the IS-41 SMSC interprets these values as being the address of the intended destination. Accordingly, the IS-41 SMSC formulates and sends a mobile-terminated SMDPP Invoke message using the point code and subsystem number of the routing node, rather than the destination switch.
When the routing node receives the SMDPP Invoke message, the routing node converts the mobile-terminated IS-41 SMDPP Invoke message to a mobile-originated GSM Forward Short Message message. The routing node sends the GSM MO Forward Short Message message to a GSM SMSC, which is responsible for delivering the message to the intended recipient. Because the routing node converts the mobile-terminated IS-41 messages to a mobile-originated GSM message, the receiving GSM SMSC believes the message to have originated from a GSM MSC receiving a message from a mobile station. As a result, the GSM SMSC simply delivers the message to its intended recipient without further involvement from the routing node.
According to yet another aspect, a routing node according to an embodiment of the present invention is capable of handling call signaling between IS-41 and GSM subscribers to establish calls between the subscribers without translating every message from IS-41 to GSM and vice versa. This applies particularly in the case where the technology, i.e., IS-41 or GSM, of the subscriber being called is not known by the MSC handling the call. The functionality for setting up calls is similar to that described above for delivering short message service messages in that when the routing node receives a location request of and the receiver uses a different application-layer mobile communications protocol than the sender, the routing node responds to the location request with the GSM or IS-41 Routing Number (RN). The sending MSC receives the location request response and sends an IAM message to the MSC serving the intended recipient. Because the routing node functions as pseudo-HLR, rather than simply a protocol converter, the routing node has a lower processing load than that of a conventional message routing gateway and reduces network traffic.